Abstract: Various disclosed embodiments provide illustrative interferometers, optical phase locked loops, laser systems, interferometry methods, and phase locked loop methods. In illustrative embodiments, light from a laser is split into a first arm and a second arm. Light in an arm chosen from the first arm and the second arm is time delayed. The light in the first arm is split into third, fourth, and fifth arms. The light in the second arm is split into sixth, seventh, and eighth arms. Light in the seventh and eighth arms is phase shifted relative to light in the sixth arm. Light in the third, fourth, and fifth arms is combined with light in the sixth arm and phase shifted light in the seventh and eighth arms, respectively. A frequency correction signal for the laser is generated.

Abstract: An aircraft imaging system for night and day imaging at ranges up to and in excess of 100 km with resolution far exceeding the diffraction limit. In a preferred embodiment two separate techniques are utilized on an aircraft to provide for night and day surveillance. The first technique is to provide a multi-aperture active imaging system for daylight imaging. The second technique is to provide a multi-aperture passive imaging system for day and night imaging. In preferred embodiments both techniques are utilized on the aircraft.